Under Microsoft browsers IE9, IE10, IE11 & Edge, the .CSS definitions dealing with the font-size -to- line-height attribute relationship, when set by using relative unit values (em, rem) with a precision of more than two (e.g. 0.8750em), are automatically rounded to only 2 digits after the decimal point (e.g. 0.87em). This is by design according to Microsoft themselves.
In a nutshell - For wiki-Foundation visitors using the affected Microsoft browsers, this means the expected Vector [calculated] defaults resulting in a font-size of 14px (16 × 0.8750 = 14) and a line-height of 22.4px (14 × 1.6 = 22.4) are actually rendering a font-size of 13.93px (16 × 0.87 = 13.93) and a line-height of 22.28px (13.93 × 1.6 = 22.28) for starters. Plus, any .css selectors that are calculated &/or defined based on &/or inherited from the current defined entry (illustrated above) will also be increasingly "off" compared to non-Microsoft browser users.
A simple change in the current Vector stylesheet should both begin to address this bug for IE 9, 10, 11 & Edge users while continuing the current "support" for [as far as I've tested] IE8 at the minimum. Applying the "workaround" might even rectify all sorts of reported "mis-alignments" & such for affected users
.mw-body-content { position: relative; font-size: 0.8750em; line-height: 1.6; z-index: 0; }
.mw-body-content { position: relative; font-size: 0.8750em; font-size: calc(1em * 0.8750 ); line-height: 1.6; z-index: 0; }
Version: 1.26+